Solar cyclicity during the epoch of the Spörer minimum – Significant obscurity

Three radiocarbon and two beryllium records were studied for the period of the Spörer minimum (CE 1432–1552). Wavelet, Fourier, correlation and principal component analysis was applied to these time series. It was shown that the event of CE 1460 yr is the most notable incident that took place during the Spörer minimum. It is, however, difficult to answer the question of whether any cyclicity of solar activity persisted during this period. A weak quasi 22-year periodicity may be present in the radiocarbon series during the entire Spörer minimum, but it is absent in 10Be records. Some evidence for weak time variations with scales 6–7 years, 9–13 years and ca 60 years were found, but this is uncertain. Obtaining and analyzing new independent proxies of solar activity is necessary to clarify the issue.